• Journal of Microbiology and Biotechnology
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• v.32 no.12
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• pp.1547-1552
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• 2022

β-Amyrin is a pentacyclic triterpene widely distributed in leaves and stems worldwide. The ability of β-amyrin to induce the production of reactive oxygen species (ROS) in microorganisms suggests its potential as an antimicrobial agent. Thus, this study aimed to elucidate the antibacterial mode of action of β-amyrin. We treated Escherichia coli cells with β-amyrin and found that it triggered ROS accumulation. Excessive stress caused by ROS, particularly hydroxyl radicals, induces glutathione (GSH) dysfunction. GSH protects cells from oxidative and osmotic stresses; thus, its dysfunction leads to membrane depolarization. The resultant change in membrane potential leads to the release of apoptotic proteins, such as caspases. The activated caspases-like protein promotes the cleavage of DNA into single strands, which is a hallmark of apoptosis-like death in bacteria. Apoptotic cells usually undergo events such as DNA fragmentation and phosphatidylserine exposure, differentiating them from necrotic cells, and the cells treated with β-amyrin in this study were positive for annexin V and negative for propidium iodide, indicating apoptosis-like death. In conclusion, our findings suggest that the antibacterial mode of action of β-amyrin involves the induction of ROS, which resulted in apoptosis-like death in E. coli.

• Biomolecules & Therapeutics
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• v.31 no.4
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• pp.359-369
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• 2023

Dependence receptors are a group of receptor proteins with shared characteristics of transducing two different signals within cells. They can transduce a positive signal of survival and differentiation in the presence of ligands. On the other hand, dependence receptors can transduce an apoptosis signal in the absence of ligands. The function of these receptors depends on the availability of their ligands. Several receptor tyrosine kinases (RTKs) have been reported as dependence receptors. When cells undergo apoptosis by dependence receptors, the intracellular domain of some RTKs is cleaved by the caspases. Among the RTKs that belong to dependence receptors, we focused on eight RTKs (RET, HER2, MET, ALK, TrkC, EphA4, EphB3, and c-KIT) that are cleaved by caspases. In this review, we describe the features of the receptors, their cleavage sites, and the fate of the cleaved products, as well as recent implications on them being used as potential therapeutics for cancer treatment.

• Journal of Life Science
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• v.23 no.9
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• pp.1118-1125
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• 2013

Naringenin, a naturally occurring citrus flavonone, is a potentially valuable candidate for cancer chemotherapy. However, the cellular and molecular mechanisms responsible for its anticancer activity are largely unknown. In the present study, we attempted to elucidate the mechanisms responsible for naringenin-induced apoptosis in human leukemic U937 cells. We found that naringenin markedly inhibited the growth of U937 cells by decreasing cell proliferation and inducing apoptosis, which was associated with the activation of caspases. A pan-caspase inhibitor, z-VAD-fmk, significantly inhibited naringenin-induced U937 cell apoptosis, indicating that caspases are key regulators of apoptosis in response to naringenin in U937 cells. Although the levels of antiapoptotic Bcl-2 and proapoptotic Bax proteins remained unchanged in naringenin-treated U937 cells, Bcl-2 overexpression attenuated naringenin-induced apoptosis. Furthermore, combined treatment with naringenin and HA14-1, a small-molecule Bcl-2 inhibitor, effectively increased the apoptosis through enhancement of XIAP down-regulation, Bid cleavage, and caspase activation, suggesting that the synergistic effect was at least partially mediated through the death receptor-mediated apoptosis pathway.

• Journal of Life Science
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• v.25 no.11
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• pp.1255-1264
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• 2015

Cnidium officinale, a traditional herb, has diverse beneficial pharmacological activities, such as anti-inflammatory, antioxidant, anticancer, and antiangiogenesis effects. However, the cellular and molecular mechanisms of apoptosis by C. officinale are poorly defined. The present study investigated the proapoptotic effects of water, ethanol, and methanol extract of C. officinale (WECO, EECO, and MECO, respectively) in human leukemia U937 cells. The antiproliferative activity of EECO was higher than that of WECO and MECO. The antiproliferative effect of EECO treatment in U937 cells was associated with the induction of apoptotic cell death, including increased populations of annexin-V positive cells, the formation of apoptotic bodies, DNA fragmentation, and increased numbers of cells with a loss of mitochondrial membrane potential (MMP, Δψm). EECO-induced apoptotic cell death was associated with upregulation of death receptor 4 (DR4) and down-regulation of cellular inhibitor of apoptosis protein-1 (cIAP-1), Bcl-2, and total Bid. The EECO treatment also induced the proteolytic activation of caspases (-3, -8, and -9), and degradation of caspase-3 substrate proteins, such as poly(ADP-ribose) polymerase (PARP), β-catenin, and phospholipase C-γ1 (PLCγ1). In addition, the EECO treatment effectively activated the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. However, compound C, a specific inhibitor of AMPK, significantly reduced EECO-induced apoptosis. These results indicate that AMPK is a key regulator of apoptosis in response to EECO in human leukemia U937 cells.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.6
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• pp.835-842
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• 2016

The phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway plays a crucial role in cancer occurrence by promoting cell proliferation and inhibiting apoptosis. In the present study, we evaluated the effect of a PI3K inhibitor, LY294002, on the chemosensitivity of gastric cancer cells to cordycepin, a predominant functional component of the fungus Cordyceps militaris, in AGS human gastric cancer cells and investigated possible underlying cellular mechanisms. Our results revealed that cordycepin inhibited viability of AGS cells in a concentration-dependent manner and induced apoptosis, as determined by apoptotic cell morphologies and fluorescence-activated cell sorting analysis associated with attenuated activation of the PI3K/Akt signaling pathway. Treatment with cordycepin in combination with a subtoxic concentration of LY294002 enhanced cordycepin-induced cytotoxicity and apoptotic potentials in AGS cells. Sensitization of LY294002 to cordycepin-induced apoptosis was accompanied by activation of caspases (caspases-3, -8, and -9) and was concomitant with poly(ADP-ribose) polymerase cleavage. Moreover, LY294002 up-regulated pro-apoptotic Bax and enhanced truncation of Bid in cordycepin-treated AGS cells, which was connected with increased loss of mitochondrial membrane potential and release of cytochrome c from mitochondria to the cytosol. Taken together, these results indicate that inhibition of the PI3K/Akt signaling pathway could augment cordycepin-induced apoptosis in human gastric cancer cells by up-regulating caspase activity through mitochondrial dysfunction.

• Journal of Life Science
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• v.31 no.10
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• pp.954-959
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• 2021

Apoptosis is an important mechanism that regulates cellular populations to maintain homeostasis, and the caspases, a family of cysteine proteases, are key mediators of the apoptosis pathway. Caspase-8 is an initiator caspase of the extrinsic apoptotic pathway, which is initiated by extracellular stimuli. Caspase-8 have two conserved domains, N-terminal tandem death effector domains (DED) and C-terminal two catalytic domain, which are important for this extrinsic apoptosis pathway. In extrinsic apoptosis pathway, death receptors which members of TNF superfamily are activated by binding of death receptor specific ligands from cell outside. After the activated death receptors recruit adaptor protein Fas-associated death domain protein (FADD), death domains (DD) of death receptor and FADD bind to each other and FADD combined with death receptor recruits procaspase-8, a precursor form of caspase-8. The DED of FADD and procaspase-8 bind to one another and FADD-bound procaspase-8 is activated by cleavage of the prodomain. This death receptor-FADD-caspase-8 complex called death inducing signaling complex (DISC). Cellular FLICE-inhibitory proteins (c-FLIPs) regulate caspase-8 activation by acting both anti- and pro-apoptotically, and caspase-8 activation initiates the activation of executioner caspases such as caspase-3. Finally activated executioner caspases complete the apoptosis by acting critically DNA degradation, nuclear condensation, plasma membrane blebbing, and the proteolysis of certain caspase substrates.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2003.04a
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• pp.39-55
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• 2003

1. Extracts of the leaves of Eurya emarginata markedly inhibited the growth of leukemia cells such as HL-60, KG-1, U937, K562, and Jurkat. 2. When HL-60 cells were treated with the extract, DNA fragmentation, morphological changes and sub-G1 hypodiploid cells were observed. The expressions of c-myc mRNA were also dramatically decreased. 3. Cornoside and Eutigoside were isolated from the leaves of Eurya emarginata. 4. Eutigoside induced apoptosis through down-regulation of Bcl-2 expression and activation of caspases.

• Proceedings of the Korean Society of Life Science Conference
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• 2007.10a
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• pp.43.2-43.2
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• 2007

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• Animal cells and systems
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• v.5 no.4
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• pp.267-274
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• 2001

Calpains are a family of cysteine proteases existing primarily in two forms designated by the $Ca^{2+}$ concentration needed for activation in vitro, $\mu$-calpain (calpain-I) and m-calpain (calpain-II). The physiologica1 roles of calpains remain unclear. Many groups have proposed a role for calpains In apoptosis, but their patterns of activation are not well characterized. Calpains have been implicated in neutrophil apoptosis, glucocorticoid-induced thymocyte apoptosis, as well as many other apoptotic pathways. Calpain activation in apoptosis is usually linked upstream or downstream to caspase activation, or in a parallel pathway alongside caspase activation. Calpains have been suggested to be involved in DNA fragmentation (via endonuclease activation), but also as effector proteases that cleave cellular proteins involved in DNA repair, membrane associated proteins and other homeostatic regulatory proteins. Recently, our laboratory demonstrated $\mu$-calpain activation in NAD(P)H: quinone oxidoreducatse 1 (NQO1)-expressing cells after exposure to $\beta$-lapachone, a novel quinone and potential chemo- and radio-therapeutic agent. Increased cytosolic $Ca^{2+}$ in NQO1-expressing cells after $\beta$-lapachone exposures were shown to lead to $\mu$-calpain activation. In turn, $\mu$-calpain activation was important for substrate proteolysis and DNA fragmentation associated with apoptosis. Upon activation, $\mu$-calpain translocated to the nucleus where it could proteolytically cleave PARP and p53. We provided evidence that $\beta$-lapachone-induced, $\mu$-calpain stimulated, apoptosis did not involve any of the known caspases; known apoptotic caspases were not activated after $\beta$-lapachone treatment of NQO1-expressing cells, nor did caspase inhibitors have any effect on $\beta$-1apachone-induced cell death. Elucidation of processes by which $\beta$-1apachone-stimulated $\mu$-calpain activation and calpains ability to activate endonucleases and induce apoptosis independent of caspase activity will be needed to further develop/modulate $\beta$-lapachone for treatment of human cancers that over-express NQO1.

• Molecules and Cells
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• v.26 no.2
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• pp.152-157
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• 2008

Caspases play critical roles in the execution of apoptosis. Caspase-3 and caspase-7 are closely related in sequence as well as in substrate specificity. The two caspases have overlapping substrate specificities with special preference for the DEVD motif. However, they are targeted to different subcellular locations during apoptosis, implying the existence of substrates specific for one or other caspase. To identify new caspase-7 substrates, we digested cell lysates obtained from the caspase-3-deficient MCF-7 cell line with purified recombinant caspase-7, and analyzed spots that disappeared or decreased by 2-DE (we refer to this as the caspase-7 degradome). Several proteins with various cellular functions underwent caspase-7-dependent proteolysis. The substrates of capase-7 identified by the degradomic approach were rather different from those of caspase-3 (Proteomics, 4, 3429-3435, 2004). Among the candidate substrates, we confirmed that Valosin-containing protein (VCP) was cleaved by both capspase-7 and caspase-3 in vitro and during apoptosis. Cleavage occurred at both $DELD^{307}$ and $DELD^{580}$. The degradomic study yielded several candidate caspase-7 substrates and their further analysis should provide valuables clues to the functions of caspase-7 during apoptosis.